1. Field of the Invention
This invention concerns an underground tank fill pipe combination of elements that apply to special protection thereof. It is especially applicable to a fill pipe arrangement that has the top underground and subject to rainwater immersion.
2. Description of the Prior Art
In the past there has been a suggestion for making use of a particular check valve in an arrangement with the vents on marine vessels so as to avoid any sea water from wave action entering the vents. Such a suggestion is embodied by the U.S. Pat. No. 1,851,084, M. W. Brown et al, Mar. 29, 1932. However, this application is concerned with the conditions relating to an underground tank fill tube that has its opening beneath ground level so that collection of rain water tends to inundate the fill pipe. Under such conditions, and when a closure for the fill pipe is employed which has an atmospheric pressure maintenance structure, it would be possible for the rain water to enter the tank through such pressure maintenance opening.
The use of a pressure maintenance arrangement, as indicated above, is required when a leak detection system is being employed to measure the level of product in the underground tank, over an extended period of time. This is because the leak detection indications would be invalidated or inaccurate if during the extended measurement time a rain storm had blocked the atmospheric pressure maintenance opening.
Consequently, it is an object of this invention to provide a combination with the fill pipe of an underground tank that is below ground level (and subject to immersion by rain water) to include an automatic closing of the atmospheric pressure maintenance opening upon rain water rising above a given level. Also, the indication of such blockage is obtained by reason of the construction of the system for so blocking the rain water.